[OSM-talk] Units convention (Was: Mapping canals)

[Greg]

I hope I'm not missing the point here but surely the maps should use a unit 
convention for each type of measure. Say metric for distance (be it from 
place to place or contour heights or sea depth) and then the user can choose 
to render it as they prefer?

Without intimate knowledge of this project and as a new visitor, I guess I had 
some preconceptions about it. I thought in these days of XML and model-view 
separation, the map would be merely a tag hierarchy for a geographical 
taxonomy and just describe the positioning of things in a spherical 
coordinate space and some meta info about each element (name, classification, 
type, description, Dublin Core data* )? The rendering or view of that space 
should be a completely separate process. If that's true, then the distances 
and all other measures will be expressed inside the notation in a 
self-consistent way (e.g. metric...)  and the user can choose to render them 
in whichever way they require at the time: colour intensity, miles, multiples 
of the distance between their ears, whetever they like. Perhaps the default 
for an application rendering the map should be to convert the units according 
to the locale settings of the host operating system?

The same principle surely would also apply to other aspects of the rendering, 
such as the icon set for road signs or the fill pattern for orchards or even 
the projection type (if any) used**. That way, the map could be rendered via 
some XSLT as a graph or filtered down to an element set of particular 
interest. Perhaps, the user prefers to store and manipulate vector on the 
server, and convert it on the fly  to their own style of bitmap on the 
client? Or use VRML instead of SVG or SVG instead of Flash or Flash instead 
of JPG. etc...

Another advantage would be the ability to search a graphical space by not just 
the pre-canned names but all the available metadata or its derived data.

I have the feeling that I'm about to kick off a storm of protest that 
everything I've described is already in place but just in case it's not, I'm 
going to post this anyway

I look forward to an interesting chat. Flame away, I'm feeling toasty 
already ;o)

Cheers,

Greg 

*http://en.wikipedia.org/wiki/Dublin_Core
**http://en.wikipedia.org/wiki/Map_projection
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